Tiny cause, big problem

Health: The invisible -- and nearly invincible -- dust mite may cause allergies and asthma.

August 15, 1999|By Patricia Meisol | Patricia Meisol,Sun Staff

It's hot hot hot, and the dust is flying. Dust mites feed with gusto this time of year, when humidity goes up and down and the air conditioner goes on and off. A few hundred thousand invisible spidery insects creeping around bed sheets and pillows are bad enough to consider. Knowing the waste from these microscopic critters does the real damage drives even the cleanest people to obsession.

Dust mites are so tiny they weren't detected indoors until the 1960s. And as modern indoor living has developed over the last three decades, they've become the bane of doctors and parents. Exposure to dust mites may lead to allergies in young children, and indoor allergies are known to trigger asthma.

Now researchers are blaming dust mites for long-term lung damage in children.

The situation is so serious that experts who educate allergy patients now urge families to rid their child's bedroom of any and all dust collectors, including the very things most commonly displayed in children's bedrooms: stuffed animals and books.

Dust mites are the kin of spiders. They eat dead-skin flakes, animal dander and molds. They live in bedding, upholstered fabrics and carpet. They like it moist and warm. They can be controlled but never eliminated with regular cleaning, which includes wiping surfaces with a damp rag and washing or dry cleaning curtains and bedding.

Mite feces contain an allergen that causes wheezing and coughing, and Dutch researchers reported last spring in the Journal of the American Lung Association that it may also reduce lung capacity in the long term. In Britain, meanwhile, doctors have discovered how dust-mite allergens penetrate lungs: They attack the adhesive between cells of the lung's lining, riddling it with holes. The discovery led to cheers in the research community -- once scientists know how the damage is done, they can propose ways to prevent it.

In a summer that comes after a mild winter and a spring that saw little rain, doctors report more and more patients with breathing problems that may be caused by dust mites. Asthma, one of the most serious allergy-related problems, is more prevalent than ever.

One theory is the modern lifestyle; many people spend most of their time indoors watching television or playing video games and inhaling dust.

Another is the increase of diesel particulate emissions. The growth of asthma has paralleled the growth of diesel vehicle sales.

A third theory is cockroaches, or their saliva; they taste their way across the floor in the dark of night.

"It's disgusting!" says Dr. John Bacon, assistant professor of pediatrics at the University of Maryland and a Towson pediatric allergist.

He offers another newly advanced idea, that cells that once directed their energy to fighting off infections when these were more common have taken on new jobs and new attributes, including inducing allergies. This could explain the growth of ragweed allergy, for instance.

The majority of people with allergies develop them from exposure to dirt or dust in childhood or adolescence.

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